BR112014023488B1 - oxidation method of an organic compound present in soil, groundwater, process water or waste water - Google Patents

Abstract

ACTIVATION OF PERSULPHATES BY ORGANIC ACIDS. The present invention is directed to a method of oxidizing an organic compound present in soil, groundwater, process water or waste water, comprising contacting such an organic compound with a persulfate and an organic acid selected from the group consisting of ascorbic acid, formic acid , oxalic acid, lactic acid, citric acid, where the molar ratio of organic acid to persulfate is between 1: 100 and 3: 1.

Description

Field of the Invention

[0001] The present invention is directed to a method of oxidizing an organic compound present in soil, groundwater, process water or waste water, comprising contacting such an organic compound with a persulfate and an organic acid selected from the group consisting of ascorbic acid , formic acid, oxalic acid, lactic acid, citric acid, where the molar ratio of organic acid to persulfate is between 1: 100 and 3: 1.

Fundamentals of the Invention

[0002] The presence of volatile organic compounds (“VOCs”), semi-volatile organic compounds (“SVOCs”) or pesticides in subsurface soils and groundwater is an extensive and well-documented problem in industrialized and industrializing countries. Many VOCs and SVOCs are compounds that are toxic or carcinogenic, are generally able to move through the soil under the influence of gravity and serve as a source of water contamination by dissolving in water passing through the contaminated soil. Illustrative of such organic contaminants are compounds such as trichlorethylene (TCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA), carbon tetrachloride, chloroform, chlorobenzenes, benzene, toluene, xylene, ethyl benzene, ethylene bromide, tertiary methyl butyl ether, polyaromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxane, nitrosodimethyl amine, and methyl tert-butyl ether.

[0003] And many cases discharge of these compounds in the soil leads to contamination of aquifers resulting in potential public health impacts and degradation of groundwater sources for future use. Treatment and remediation of soils contaminated with VOC or SVOC compounds must be expensive, require considerable time, and in many cases be incomplete or unsuccessful. Treatment and remediation of volatile organic compounds that are either partially or completely immiscible with water (eg, Non-Aqueous Phase Liquids or NAPLs) has been particularly difficult. Also treatment of highly soluble, but biologically stable organic contaminants such as MTBE and 1,3-dioxane are also very difficult with many conventional remediation technologies. This is particularly true if these compounds are not significantly naturally degraded, either chemically or biologically, in soil environments. Subsurface NAPLs can be toxic to humans and other organisms and can slowly release dissolved aqueous or volatile organic compounds in the gas phase into long-term groundwater (eg, decades or more) sources of subsurface chemical contamination. In many cases, contaminants from subsurface groundwater plumes can extend hundreds to thousands of feet from the source of chemicals resulting in extensive subsurface contamination. These chemicals can then be transported in sources of drinking water, lakes, rivers, and even basements of houses through the volatilization of groundwater.

[0004] The American Environmental Protection Agency (USEPA) has established maximum concentration limits for various hazardous compounds. Very low and strict drinking water limits have been placed on many halogenated organic compounds. For example, the maximum concentration limits for solvents such as trichlorethylene, tetrachlorethylene, and carbon tetrachloride were set at 5 .mu.g / L, while the maximum concentration limits for chlorobenzenes, polychlorinated biphenyls (PCBs), and ethylene dibromide were established by USEPA at 100 mu.g / L, 0.5 .mu / L, and 0.05 .mu.g / L, respectively. Consequently, there is a need for improved methods to achieve environmental remediation.

[0005] Curtin et al, “Ascorbate-induced oxidation of formate by peroxodisulfate: product yields, kinetics and mechanism”, Res. Chem. Intermed., Vol. 30, No. 6, pp. 647-661 (2004) discloses that the constant rate (ki) of reaction of persulfate with ascorbic acid to produce an SO4-2 radical is 0.02, thus indicating that ascorbic acid is ineffective to activate persulfate.

[0006] Huling et al, “Groundwater Sampling at ISCO Sites: Binary Mixtures of Volatile Organic Compound and Persulfate, Ground Water Monitoring & Remediation 31”, no. 2 / Spring 2011 / pages 72-79 discloses the use of high levels of ascorbic acid (from 4: 1 molar fractions or greater of ascorbic acid: persulfate) to preserve samples of sodium persulfate and VOCs for analytical purposes. The addition of such proportions of ascorbic acid deactivates the persulfate without significantly reducing the amounts of VOCs (benzene, toluene, m-xylene, perchlorethylene and trichlorethylene) present in such samples, further suggesting that ascorbic acid is ineffective to activate persulfate in remediation situations .

[0007] Consequently, it is completely unexpected that the addition of minor proportions of ascorbic acid and / or other organic acids selected from the group comprised of formic acid, oxalic acid, lactic acid and citric acid will effectively activate persulfate as well as organic contaminants contacted with such mixture will be effectively oxidized.

Summary of the Invention

[0008] The present invention is directed to a method of oxidizing an organic compound present in soil, groundwater, process water or waste water, comprising contacting such an organic compound with a persulfate and an organic acid selected from the group consisting of ascorbic acid , formic acid, oxalic acid, lactic acid, citric acid, where the molar ratio of organic acid to persulfate is between 1: 100 and 3: 1.

Description of Preferred Modalities

[0009] The present invention is directed to a method of oxidizing an organic compound present in soil, groundwater, process water or waste water, comprising contacting such an organic compound with a persulfate and an organic acid selected from the group consisting of ascorbic acid , formic acid, oxalic acid, lactic acid, citric acid, where the molar ratio of organic acid to persulfate is between 1: 100 and 3: 1.

[0010] The present invention is a method for remediation of soil, sediment, clay, rock, and the like (here collectively referred to as "soil"), groundwater (eg, water found below ground in crevices and spaces in the soil, sand and rocks); process water (eg water resulting from various industrial processes) or waste water (eg water containing household or industrial waste) contaminated with volatile organic compounds, semi-volatile organic compounds, pesticides or herbicides. In addition, it can be used to treat sludge, sand or pitch.

[0011] Illustrative of the organic contaminants that can oxidize by the process of this invention are trichlorethylene (TCE), vinyl chloride, tetrachlorethylene (PCE), methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA), carbon tetrachloride, chloroform, chlorobenzenes, benzene, toluene, xylene, ethyl benzene, ethylene dibromide, tertiary methyl buryl ether, polyaromatic hydrocarbons, polychlorobinophiles, phthalates, 1,4-dioxane, nitrosodimethyl amine, and methyl tert-butyl ether.

[0012] Persulfates that can be used include mono- and dipersulfates, as well as mixtures thereof. Preferably, dipersulfates such as sodium persulfate, potassium persulfate, and / or ammonium persulfate are employed, with sodium dipersulfate being particularly preferred.

[0013] The organic acid that can be used in the practice of this invention is selected from the group consisting of ascorbic acid, formic acid, oxalic acid, lactic acid and citric acid. Preferably such an organic acid is ascorbic acid. As used herein, the term "organic acid" is intended to include compounds, such as salts, that will form such an acid in use under contact with water, provided that such an acid-forming compound does not comprise another component (such as an ion of divalent or trivalent metal) that is known to activate persulfate.

[0014] The molar fraction between organic acid and persulfate is typically between 1: 100 and 3: 1. Preferably, such a molar fraction is between 1:50 and 2.5: 1, and is more preferably between 1:10 and 2: 1.

[0015] In the practice of the present invention, persulfate and organic acid can be contaminated in an aqueous composition before treatment and co-injected into the environment to be treated. Alternatively, such components can be sequentially or simultaneously injected into such an environment.

[0016] When used in the environmental remediation of soil and / or groundwater, persulfate must be used in sufficient quantities to satisfy the soil's oxidant demand, compensating for any decomposition and oxidizing and destroying most if not all organic compounds. Soil oxidant demand, (SOD), is the loss of persulfate due to the reaction with soil matrix components as well as through self-decomposition of persulfate, as well as the oxidizing demand for chemicals, and to compensate for any decomposition of the peroxygen.

[0017] A method for calculating the preferred amount of persulfate to be used per unit mass of soil (for an identified volume of soil at the site) is to first determine the minimum amount of persulfate needed to fully satisfy the demand for soil oxidizer per unit of uncontaminated soil mass. A sample of contaminated soil of the identified volume of soil is then treated with the predetermined amount (per unit mass) of persulfate, and the minimum amount of persulfate required to eliminate the organic compounds in which the treated sample is then determined. Stoichiometry of the chemical reaction governs the mass / mass fractions and thus the total amount required to achieve the desired result. In fact, the amount of persulphate injected at several locations in a single contaminated location will vary depending on what is learned from the core samples and other techniques for mapping subsurface conditions. SOD can also be calculated according to the formula (I): SOD = V * (Co - Cf) / Ms (I) Where V = volume of groundwater used in the sample Co = initial concentration of persulfate at time 0 Cf = concentration of persulfate after 48 hours Ms = mass of soil used in the sample

[0018] Depending on the type of soil, target compounds, and other oxidant demands on site, the concentrations of persulfate in the solution used in the present invention can vary from about 0.5 mg / L to more than about 450,000 mg / L . Preferred concentrations are a function of soil characteristics, including site-specific oxidant demands. Hydrogeological conditions govern the fraction of movement of chemicals through the soil, and these conditions must be considered together with the soil chemistry to understand how to best perform the injection. The techniques for making these determinations and making the injections are well known in the art. For example, wells or holes can be drilled at various locations and around the site with suspected contamination to determine, as close as possible, where the contamination is located. Core samples can be taken, being careful to protect the samples from atmospheric oxidation. The samples can then be used to determine soil oxidant demand, chemical oxidant demand (eg VOC) and the oxidation stability existing on the subsurface. The precise chemical compounds in the soil and their concentration can be determined. Contaminated groundwater can be collected. Oxidizers can be added to groundwater collected during laboratory treatability experiments to determine which compounds are destroyed, in what order and to what degree, in groundwater. It can be determined whether the same oxidants are capable of destroying those chemicals in the soil environment.

[0019] The objective is the concentration of persulfate in the injected solution to be only necessary to result in the reaction of persulfate traveling through the contamination area requiring treatment in sufficient quantity to oxidize the contaminants present. (The zone of saturated soil is the zone of soil that is below the water table and is completely saturated. This is the region in which groundwater exists and drains). In certain areas of saturated soil where the natural groundwater speed is too low for treatment purposes within a certain time interval, the groundwater speed can be increased by increasing the flow rate of the injected persulfate solution or installation of the wells groundwater extraction to direct the flow of injected persulfate solution. Certain soils to be treated may be in unsaturated areas and the method of persulfate injection may be based on infiltration or dripping of the persulfate solution on the subsurface to provide sufficient contact of the soils with the injected chemicals.

[0020] In addition, the persulfate and activator can be applied and distributed across soils, in either saturated or unsaturated conditions through the use of a soil mixing process. Such a process makes use of soil mixers in situ, such as rotating drum heads, prognosis devices or excavator / backhoe mixing, to mix the oxidizer and activator in the soil and provides a more homogeneous mixture, allowing improved contact between the contaminant and the oxidizer.

[0021] The process of the present invention can be employed in situ or ex situ. For in situ soil treatment, injection rates should be chosen based on hydrogeological conditions, that is, the ability of the solution to oxidize to displace, mix and disperse with existing groundwater and move through the soil. In addition, injection rates should be sufficient to satisfy the demand for soil oxidant and the demand for chemical oxidant in a realistic time frame. It is advantageous to clean locations in both a cost-effective and time-efficient manner. Careful assessment of site parameters is crucial. It is well known that soil permeability can change rapidly both as a function of depth and lateral dimension. However, injection well locations are also site specific. Proper application of any remediation technology depends on knowledge of the subsurface conditions, both chemical and physical, and this process is no different in this respect.

[0022] The following Examples are provided to further illustrate the invention, but are not intended to limit the scope of the invention in any way. Examples Example 1

[0023] Benzene and trichlorethylene were added to tap water to produce a test solution comprising 6.3 mg / L benzene and 1.5 ppm TCE. This test solution was poured into 40 ml flasks and sodium dipersulfate (PS) added to a final concentration of 5.0 g / L. Ascorbic acid (AA) was added in solid form to these AA / PS fractions listed in Table 1 below. Control samples containing only the test solution, and containing only 5.0 g / L of PS were also prepared. These samples were sealed without leaving any empty space. The samples were stored at 25 ° C for one day.

Exemplo 2[0024] After such storage, the concentrations of benzene and TCE present in each sample vial were determined using GC-MS (Shimadzu GCMS- QP2010) and a Purge & Trap sample concentrator (OI Analytical 4560), according to EPA methods 5030 and 8260. The results of such tests are summarized in Table 1. Table 1

Example 2

[0025] The procedure of Example 1 was repeated, except that the samples stored at 2 ° C. The results of such tests are summarized in Table 2. Table 2

[0026] A comparison of Table 1 and Table 2 shows that the process of this invention is effective at low temperatures of less than 20 ° C, and more typically of less than 10 ° C in which the majority of environmental remediation in situ should take place. Example 3

[0027] Benzene and trichlorethylene were added to tap water to produce a test solution comprising 32.7 mg / L benzene and 18.3 ppm TCE. The test solution was then divided into two parts, and sodium dipersulfate (PS) was added to one part at a final concentration of 5.0 g / L, and the second part at a final concentration of 1.0 g / L . These test solutions were poured into 40 ml flasks, to which ascorbic acid (AA) was added in solid form to those AA / PS fractions listed in Table 3 below. Control samples containing only the test solution and containing only 5.0 g / L of PS and 1.0 g / L of PS were also prepared. The samples were sealed without leaving any empty space. The samples were then divided into two parts. One part was stored at 25 ° C for two days, and the second at 2C for two days.

[0028] After such storage, the concentrations of benzene and TCE present in each sample vial were determined using GC-MS (Shimadzu GCMS- QP2010) and a Purge & Trap sample concentrator (OI Analytical 4560), according to EPA methods 5030 and 8260. The results of each test are summarized in Tables 3-6.

[0029] The data in Tables 3 to 6 show that the process of this invention is effective at AA: PS molar fractions in the range of about 1:10 to about 3: 1. The process is effective at low temperatures (2 ° C) which are often found in environmental remediation.

Example 4

[0030] Benzene was added to the tap water to produce a test solution comprising 9.1 mg / L of benzene. This test solution was poured into 40 ml flasks and sodium dipersulfate (PS) was added to a final concentration of 5.0 g / L. Those indicated organic acids were added to the Acid / OS fractions listed in Table 7 and Table 8 below. Control samples containing only the test solution and containing only 5.0 g / L of PS were also prepared. The samples were sealed without leaving any empty space. Part of the samples were stored at 25 ° C and part at 2 ° C for one week.

[0031] Samples were tested periodically for benzene concentration using GC-MS (Shimadzu GCMS-QP2010) and a Purge & Trap sample concentrator (OI Analytical 4560), according to methods EPA 5030 and 8260. The results of each test are summarized in Table 7 and Table 8.

[0032] The data in Tables 7 and 8 show that oxalic acid, citric acid, formic acid and lactic acid are all effective activators for PS, at both 2 ° C and 25 ° C.

Claims (9)

1. Method of oxidation of an organic compound present in the soil, groundwater, processing water or waste water, characterized by the fact that it comprises contacting the organic compound with a persulfate and an organic acid selected from the group consisting of ascorbic acid, formic acid , oxalic acid, lactic acid, citric acid, where the molar ratio of organic acid to persulfate is between 1:10 and 2: 1. 2. Method according to claim 1, characterized in that the persulfate is a dipersulfate. Method according to claim 2, characterized by the fact that dipersulfate is sodium persulfate. Method according to claim 1, characterized in that the organic acid is ascorbic acid. 5. Method according to claim 1, characterized by the fact that the organic compound is selected from the group consisting of trichlorethylene, vinyl chloride, tetrachlorethylene, methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane, carbon tetrachloride, chloroform, chlorobenzenes, benzene, toluene, xylene, ethyl benzene, ethylene bibromide, tert-butyl methyl ether, polyaromatic hydrocarbons, polychlorinated biphenyls, phthalates, 1,4-dioxanes, nitrosodimethyl amine and tert-butyl methyl ether. 6. Method according to claim 1, characterized by the fact that it is carried out in situ. 7. Method according to claim 1, characterized by the fact that it is performed ex situ. Method according to claim 6, characterized in that the persulfate and the organic acid are added simultaneously. Method according to claim 6, characterized in that the persulfate and the organic acid are added in sequence.